Written on Thursday, March 29, 2007 by Gemini

More than two-thirds of the world’s large cities, including Mumbai, are in areas that are vulnerable to rising sea levels because of global warming. And this puts millions of people at risk of being swamped by flooding and intense storms, according to a new study released Wednesday.

In all, 634 million people live in the threatened coastal areas worldwide – defined as those lying at less than 33 feet above sea level – and the number is growing, said the study published in the journal Environment and Urbanization.

More than 180 countries have populations in low-elevation coastal zones, and about 70 per cent of those have urban areas of more than 5 million people that are under threat, the report said.

Besides Mumbai, the other major cities at risk include Tokyo, New York, Shanghai, Jakarta, Indonesia and Dhaka.

The peer-reviewed scientific study – the first to identify the world’s lowlying coastal areas that are vulnerable to rising sea levels – said 75 per cent of all people living in vulnerable areas are in Asia, with poorer nations most at risk.

The study gives no time frame for rising sea levels or the potential flooding in individual countries. It warns, however, the solution to the problem will not be cheap and may involve relocating many people and building protective engineering structures. And, it adds, nations should consider halting or reducing population growth in coastal areas.

“Migration away from the zone at risk will be necessary but costly and hard to implement, so coastal settlements will also need to be modified to protect residents,” said Gordon McGranahan of the International Institute for Environment and Development in London, a co-author of the study.

The other two co-authors of the study are US-based Deborah Balk of the City University of New York and Bridget Anderson of Columbia University. Separately, the authoritative Intergovernmental Panel on Climate Change said – in a draft copy of a report expected to be released next week – that coastlines are already showing the impact of sea-level rise. The draft copy said about 100 million people each year could be flooded by rising seas by 2080.

In February, the IPCC warned of sea-level rises of 7-23 inches by the end of the century due to global warming, making coastal populations vulnerable to flooding and more intense hurricanes and typhoons. Asia is particularly vulnerable, the study said. The five nations with the largest total population living in endangered coastal areas are all in Asia: India, China, Bangladesh, Vietnam and Indonesia. Between 1994 and 2004, about onethird of the world’s 1,562 flood disasters occurred in Asia.

Still, Asia accounted for nearly half of the total 1,20,000 people killed by the natural calamity, the study said. “Migration away from lower coastal zones will be important, but can be difficult to implement without causing severe disruptions,” the study said. But, it added that “small settlement shifts out of lower coastal plains and onto more elevated ground can make a major difference.”